-LRB- CNN -RRB- -- The Washington Navy Yard is the home to high-level naval personnel and is the workplace for at least 3,000 service members and civilian employees . Located in the heart of Washington , D.C. , the premises include a park and many buildings .

Chief of Naval Operations Jonathan Greenert was at his residence at the Yard on Monday and was evacuated , CNN 's Barbara Starr said .

She added that in her experience visiting the facility , security is extensive . Everyone must have clearance to be there or valid identification that allows them entry .

But she added that `` you could have all the authority in the world to be on the installation '' and still plan to do harm without detection by guards .

Read more about entering the Yard

The Yard includes the headquarters for the Naval Historical Center and the U.S. Navy Judge Advocate General 's Corps , among others . It 's the headquarters for the Naval Sea Systems Command , where police said shots were fired Monday .

Capt. Mark Vandroff spoke to reporters , explaining that he and his colleagues remained in a conference room in their building -- 197 -- hunkered down until the scene was safe .

He described the building as the largest of three overseen by the Naval Sea System command , the Navy 's organization that procures and maintains ships and submarines . Building 197 houses headquarter staff , legal team , contractors , engineers and buyers of various weapon and defense systems , among others , he said .

Vandroff added that he was very happy that his staff remained calm , though they were scared as they hunkered down in a conference room . '' 'Cause we knew if we sheltered in place eventually the police would come get us , '' he said .

The Navy Museum at the Yard is open to the public . Leutze Park hosts ceremonies and offers walking tours .

The Yard has a dramatic history , its website says .

A former shipyard and ordnance plant , it 's the oldest U.S. onshore installation .

It was added to the National Register of Historic Places in 1973 and designated a National Historic Landmark three years later .

The Yard was created in 1799 by an act of Congress , the Naval History and Heritage Command says . It was envisioned as a shipbuilding and fitting facility on the Anacostia River and over the years has serviced several storied vessels , including the USS Constitution .

During the War of 1812 , the Yard burned down and was rebuilt as a weapons manufacturing hub . It has also been the scene of significant advancements in military technology . During the War of 1812 , Robert Fulton conducted research and testing on his clockwork torpedo , and in 1822 , Commodore John Rodgers built the United States ' first marine railway for the overhaul of large vessels at the Yard , according to its site .

The Yard was crucial to the defense of Washington during the Civil War , according to its website . President Abraham Lincoln frequently visited the Yard many times , according to the Yard 's site . The body of Lincoln 's killer , John Wilkes Booth , was examined and identified on a ship moored at there .

Amid World War I , the Yard made Navy ordnance , including the 14-inch naval railway guns used in France in the war .

In the years after World War II and into the Cold War era , the Yard 's military role lessened .

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The U.S. Navy Yard is home to high-level naval personnel

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Many service members and civilian employees work there

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Security is tight at the Yard , CNN 's Barbara Starr reports